Generally so-called catalytic heaters, which effect catalytic oxidation of hydrocarbons on contact, have an active phase constituted by the noble metals of group VIII (Periods 5 and 6) of the PERIODIC TABLE OF THE ELEMENTS (see the Periodic Chart of the Elements at pages 448 and 449 of the Handbook of Chemistry and Physics, 41st Edition 1959/60). The most commonly used of these platinum-group elements is platinum itself because of its relatively high catalytic activity.
There are several disadvantages to using platinum, firstly, even when used in small quantities it is an expensive metal. Secondly, it is highly susceptible to poisoning and to coating with deposits such as carbon which develop rapidly if the support for the catalyst contains iron oxide and the gas being oxidized contains high proportions of ethylenic hydrocarbons.